Answer: The area you describe can be categorized as "light shade". I'd plant several in the container, or add a few more containers. Some of the best plants for such an area include:
Double impatiens 'Pink Ice'; boasts variegated foliage and salmon-pink flowers. The cultivar 'Red' of the Rose Parade Series produces deep-red blooms in great profusion.
Lobelia 'Queen Victoria', Fuchsia 'Gartenmeister Bonstedt', Lamiummaculatum 'White Nancy', variegated ground ivy, Hosta 'Patriot', and variegated lilyturf (Ophiopogon jaburan 'Vittatus').
You might also try coleus. With the explosion of new coleus available, there's a cultivar to fit almost any color scheme. Their leaves vary from a single, solid hue to a complex mix of colors.
Begonia 'Exotica' is a variegated begonia that lives up to its name. Its leaves are olive-green with deep-pink blotches and a metallic sheen.
The thin, deep-maroon leaves of blood leaf (Iresine lindenii) can offer textural contrast; Caladium bicolor 'Rosalie'?with deep-red-centered leaves edged in green?echoed the blood leaf.
Best wishes with your container garden!
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